readwritepriority.java

英国帝国理工学院电脑系多线程课程教学材料之十二 ---- 读取者与写入者范例（starvation修正版）

package concurrency.readwrite;

//@author: j.n.magee 11/11/96
//
// The Read Write Monitor Class - Writers priority
//
class ReadWritePriority implements ReadWrite{
  private int readers =0;
  private boolean writing = false;
  private int waitingW = 0; // no of waiting Writers.

  public synchronized void acquireRead()
             throws InterruptedException {
    while (writing || waitingW>0) wait();
     ++readers;
  }

  public synchronized void releaseRead() {
    --readers;
    if (readers==0) notifyAll();
  }

  public synchronized void acquireWrite()
             throws InterruptedException {
    ++waitingW;
    while (readers>0 || writing) wait();
    --waitingW;
    writing = true;
  }

  public synchronized void releaseWrite() {
    writing = false;
    notifyAll();
  }
}